This invention relates generally to containers for shipping general bulk liquid cargo, and more particularly to a spillage-resistant double-tank container constituted by a sea-going vessel whose single hull defines the outer tank of the container and a flexible bladder forming an inner tank received within the outer tank and roughly conforming thereto.
In transporting general bulk liquid cargo such as gasoline, crude oil and various other liquid chemicals in the cold or hot state, use is usually made of freighters, tankers or oil carriers having a single-layer hull having a hold which defines the container for the cargo. The serious problem encountered with such vessels is that should an accident or collision occur or the ship run aground, resulting in fracture or injury to the hull, the leakage of liquid into the surrounding sea may give rise to an intolerable pollution, particularly in the case of an oil spill.
Because of the international furor created by oil spills, various schemes have heretofore been proposed to minimize the danger of leakage from oil carriers. In most cases, the solution lies in a double hull vessel whose design is such that in the event of an accident or collision which impairs the structure of the outer hull, the inner hull can be expected to retain its integrity and prevent leakage of the liquid cargo held therein.
While a double hull structure affords the necessary safety factor, it represents a highly expensive solution which, if widely adopted, would render obsolute a great many single-hull vessels that are still in good working condition. Thus crude oil is presently being transported in huge sea-going carriers known as VLCC (Very Large Crude Carriers) having single hulls. The cost of replacing these vessels with double-hull structures would be enormous.